000
FXUS65 KBOU 270826
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
226 AM MDT Sat Apr 27 2024

.KEY MESSAGES...

- Significant snowfall (1 to 3 feet) for the mountains and
  foothills through tonight.

- Snow level falling to 6000 to 7000 feet MSL.

- Rainfall amounts through tonight of 1 to 3 inches for the lower
  foothills, Urban Corridor, and eastern plains.

&&

.SHORT TERM /Through tonight/...
Issued at 208 AM MDT Sat Apr 27 2024

Today, widespread precipitation will drop anchor across the
forecast area. The next upper low over the Great Basin early this
morning, is progged to shift into central CO by this evening then
into southwest NE by 12z Sunday. Moderate mid/upper level QG
ascent will develop over the northeast CO this morning, in a
diffluent and deep south/southeasterly layer. It will be moist
adiabatic through the layer, with enough instability to produce
thunderstorms as well. Consequently, heavy snow will develop in
the mountains and foothills, with the snow level around 8,000 feet
and down to around 6500 feet by later this afternoon. After
coordination with the PUB office, we moved up the timing of the
Winter Weather Advisory over the Palmer Divide to 3 AM vs 6 AM this
morning. Otherwise, no other changes to the highlights at this
time. 24-hr qpf still generating anywhere from 1 to 3 inches of
water across the forecast area.

The HRRR models do indicate a few strong storms developing over
Lincoln County this afternoon, with an upper level jet passing to
the south and east of there. SPC has a marginal risk of severe
thunderstorms this afternoon, with the main threat hail up to
quarter size. By 00z this evening, the strongest QG ascent will
shift towards NE/KS and the flow aloft should start to shift to
the north/northeast. Widespread precipitation should continue
through the evening, but the intensity should decrease. Once the
precipitation tapers off, could see patchy fog late tonight into
Sunday morning but not enough confidence in this outcome to
include it in our grids yet.

&&

.LONG TERM /Sunday through Friday/...
Issued at 208 AM MDT Sat Apr 27 2024

Upper level low will move into the Nebraska panhandle early
Sunday morning and continue to pull away from Colorado Sunday.
Wrap around rain showers are expected to linger into Sunday
morning over far northeast Colorado. In addition to this,
scattered snow showers will continue Sunday in the mountains.
Northwest flow behind the low will produce downslope conditions
along the Front Range and nearby plains. This is expected to lead
dry conditions for most of Sunday, though isolated to scattered
showers are expected to develop during the afternoon when it gets
a little unstable. Scattered snow showers continue through the day
in the mountains with up to 3 inches of snow possible.
Temperatures rebound into the upper 50s to lower 60s over
northeast Colorado.

Weak ridging in the westerly flow aloft will prevail Monday. This
will produce mild and dry conditions. Highs are expected to warm
up into the mid to upper 60s. Right behind this ridging, an upper
level trough will track across Montana and Wyoming. This wave and
the left exit region of the jet may bring showers late Monday and
Monday night to northern Colorado. A shallow cold front will also
drop south across eastern Colorado Monday night. Though highs
behind it Tuesday don`t change much from Monday. There will be a
chance for showers and storms Tuesday afternoon over the plains.

For Wednesday and Thursday, an upper level low over Idaho and
Montana digs southeast. Models are still zeroing in on the track.
This system could stay north of Colorado and track east across
Wyoming, or like the ECMWF, it could dive farther southeast into
Colorado. With this being a stronger system, even if it stays
north of Colorado, the cold front and moisture associated with it
should produce scattered showers and storms late Wednesday and
into Thursday. If this system digs farther south, a widespread
rain and mountain snow event will be possible. Temperatures trend
cooler and by Thursday and highs may only be in the 50s over
northeast Colorado.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1122 PM MDT Fri Apr 26 2024

Persistent rainfall and low cloud decks through the period. MFVR
conditions early in the period will deteriorate to IFR shortly
(after 08z) and continue through the period. There is a low
probability of a rain/snow mix at APA or BJC, which could lower
the ceilings/vsbys further. Surface winds will transition from NNW
to NE after 08z and continue that way through the rest of the
period. Sustained winds in the 8-12kt range can be expected. Once
the precipitation settles down by the end of the period, fog may
also need to be addressed in the outlook period for DEN (06-12Z
Sunday).

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until midnight MDT tonight for COZ033-034.

Winter Storm Warning until 6 AM MDT Sunday for COZ035-036.

Winter Weather Advisory until midnight MDT tonight for
COZ037-COZ041.

&&

$$

SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Cooper

NWS BOU Office Area Forecast Discussion